Metal spinning machine



R. A. PAULTON METAL SPINNING MACHINE April 7, 1964 4 Sheets-Sheet 1 Filed June '7, 1961 INVENTOR.

RICHARD A. PAULTON 2/ fG'TORNEYS April 7, 1964 Filed June 7, 1961 R. A. PAULTON METAL SPINNING MACHINE 4 Sheets-5heet 2 IN V EN TOR.

RICHARD A. PAULTON ATTORNEYS April 7, 1964 R. A. PAULTON 3,127,861 METAL SPINNING MACHINE Filed J1me 7, 1961 4 Sheets-Sheet 3 IN V EN TOR.

RICHARD A. PAULTON ATTORNEYS April 7, 1964 Filed June 7, 1961 R. A. PAULTON METAL SPINNING MACHINE 4 Sheets-Sheet 4 23 I 1 I 1% as I \,7 l I II I /I32 11 I II mmvrok. RICHARD A. PAULTON BY ATTORNEYS United States Patent 3,127,861 METAL SPINNING MACHINE This invention relates to a machine tool of unique construction and is particularly suited for metal spinning operations.

Metal spinning is a specialized drawing process in which an article having a surface of revolution is formed from a workpiece blank. The blank is held against and rotated with a mandrel having the desired shape. Forming tools are forced against the blank and moved progressively along the mandrel to force the blank to conform to the shape of the mandrel. Many items of fabrication for use in rockets and missiles, for example, nose cones and rocket motor casings, are best produced by the spinning process. Shaping of high strength materials, particularly in the large sizes required for missile components, necessitates a spinning machine capable of producing great forces between the mandrel, blank, and forming tool resulting in great stresses within the machine. The accuracy requirements dictate that the movement of the forming tool along the mandrel be accurate and relatively free from the distortive effects tending to be introduced into a machine by the production of great stresses therein during the spinning process.

It is therefore an object of this invention to provide a machine tool constructed in such a way as to eliminate much of the distortive effect that stresses, produced by a spinning operation, otherwise would have upon the guide ways which direct the forming tools along the mandrel during the spinning operation.

In is also an object of this invention to reduce the bearing pressure of the tool carriers on the guide ways along which they move, thereby reducing the wear of the guide ways and the power necessary to move the tools along the mandrel in a spinning operation.

Other objects and advantages of the present invention should be readily apparent by reference to the following specification, considered in conjunction with the accompanying drawings forming a part thereof, and it is to be understood that any modifications may be made in the exact structural details there shown and described, within the scope of the appended claims, without departing from or exceeding the spirit of the invention.

A machine constructed in accordance with the preferred form of this invention is designed to spin form an article around a vertically oriented axis of rotation. Lead screws extend upward from a base in which a driving plate, rotatable on the vertical axis, is received. These lead screws support a rigid box frame in which the forming tools are received. The box frame is held in alignment above the driving plate and around the axis of rotation by vertical guide ways which are located on columns extending from the base. The box frame is movable vertically on the lead screws during a spinning operation to move the forming tools along the mandrel. The forming tools are received in the box frame in such a way as to transmit a great amount of the reactive forces from the spinning operation to the box frame in opposing pairs of forces tending to balance one another. By maintaining the pairs of forces in a substantially balanced condition, the resultant deflective force transmitted to the vertical guide ways is reduced. Consequently, the lateral deflection of the guide ways is similarly reduced and the tool carriers are more easily maintained in their vertical position above the driving plate and along the mandrel. In addition, the bearing forces between box frame and guide ways is proportional to the unbalance of opposing forces. By reducing the forces transmitted to the guide ways, the friction drag during movement is reduced as is the wear of the guide ways.

The construction and operation of the preferred form of this invention is disclosed in the following detailed description in which reference is made to the attached drawings wherein:

FIG. 1 is a front elevation of a vertical spinning machine;

FIG. 2 is a section of the machine in FIG. 1 on line 2-2.

FIG. 3 is a section of the machine in FIG. 1 on line 3-3.

FIG. 4 is a section of a drive mechanism of the machine on line 44 of FIG. 3.

A vertical metal spinning machine is shown in FIG. 1 in a front elevational view. The machine rests on a base portion 1t) from which vertical columns 12 extend. The columns 12, as shown in FIG. 2, are spaced around a driving plate 14 which is rotatable in the base 1% on a vertical axis. Each of the columns 12 has a set of guide ways 16, 18 (FIG. 2), which are parallel to the vertical axis. A set of vertical lead screws 20 are fixed in brackets 22 connected to the columns 12 and base 10, FIGS. 1 and 2, and are parallel to the axis of rotation of the driving plate 14. The screws 20 may be of any threaded form but the preferred type is the ball screw type of well known form. For purposes of description, the screws 20 will be referred to as threaded and this is intended to represent any well known thread form. A top plate 2d is connected to the columns 12 and the upper ends of the lead screws 20 are fixed therein. The top plate 24 together with a pair of structural members 25 which are received across the columns 12 at the front and rear of the machine just below the top plate 24 tie the columns 12 and screws 20 together at the ends thereof opposite the base 10 to maintain parallelism and machine rigidity. Supported on the lead screws 20 above the base 19 is a box frame 26 in which spin forming tools 28 are supported on swivel spindles 39 for adjustment relative to the axis of rotation of the driving plate 14 and a mandrel 32 (shown in phantom) received thereon. (The swivel spindles 30 are shown in FIG. 1 in different positions for illustration of adjustability.) The position of the box frame 26 around the axis of rotation of the driving plate 14 is maintained by the vertical guide ways 16, 18 with which the box frame 26 is slidably engaged. A tailstock unit 34 is supported on the lead screws 28 above the box frame 26 and below the top plate 24. The tailstock unit 34 has a vertically oriented spindle 36 which may be adjusted therein to a lateral position such that its axis of rotation is the same as the axis of rotation. of the driving plate 14. The vertical guide ways 16, 18, with which the tailstock unit 34 is slidably engaged, furnish the lateral support to the tailstock unit 34 to hold it in this position.

In FIG. 2, the construction of the base portion 10 is shown, the base portion being analogous to a headstock of a conventional horizontal machine. The base 10 is of a general rectangular shape having end members 38 and side members 46 welded together. To give the base 1i) rigidity, web stiffening plates 42 are welded within the rectangle formed by the members 38 and 46. The base 10 is covered by a metal cover plate 44 to prevent entry of foreign matter into the base where the bearings 46 (FIG. 1) on which the rotatable drive plate 14 is supported, and the drive motor (not shown) which rotates the drive plate, are located. A pair of plates 48 are fixed across the front and rear of the base 10 and, with the side members 40, include an angle in which the columns 12 are fixed by bolts 50, 52 (not all shown). Each of the columns 12 is comprised of side plates 54 U and end plates 56which are welded together to form a rectangular cross section. The vertical guide ways 16, 18 are welded to the columns 12 and extend thereon parallel to the vertical axis of rotation of the driving plate 14. The brackets 22 are fixed to both the columns 12 and the base to form a rigid member in which the lead screws are supported. The entire machine is supported on footing members 60, 62 which are received under the rectangular base 10 and columns 12, respectively. These footing members 60, 62 have leveling screws 64 (not all shown in FIG. 2) by which the machine is adjustably positionable relative to vertical and horizontal planes.

In FIG. 3, the structural composition of the box frame 26 in which the tools 28 are supported is shown. The box frame 26 is constructed basically from front and rear rails 66 and side members 70 (one shown in FIG. 3) to form a rectangular shape. The side members 70 are built up of two parallel plates 72, 74 between which a pair of spacers 76 is received. The front and rear rails 66 each have a support bracket 7'7 fixed thereto. Each of the brackets 77 has a pair of gear boxes 78 in which a rotatable nut 80 is received. The nuts 80 are threadedly engaged with the lead screws 20 and support the weight of the box frame 26 on the screws 20. Each of the nuts 80 is rotated by a hydraulic motor 82 (FIG. 1) which is located in the respective bracket 7'7 adjacent the respective gear box 78. The nuts 88 are connected to synchros 81 (FIG. 1) which control cooperative operation of the motors 82 to maintain the nuts 80 at identical positions on the stationary lead screws 20, thereby holding the box frame 26 square relative to the guide ways 16, 18 which are embraced by brackets 85 fixed to the front and rear rails 66 to hold the frame 26 in alignment over the driving plate 14 (FIG. 2). Counter balance motors 83 are also connected to the nuts 80 to exert a force thereon which tends to balance the weight of the box frame 26 and enable the motors 82 to operate to elevate or lower the box frame with nearly equal effort. The box frame 26 is of heavy and rigid construction with the ability to contain high internal tension and compressive stresses within the members comprising it.

The detail of the connection of the hydraulic motors 82 and their connection to drive the box frame 26 is shown in FIG. 4. The hydraulic motor 82 is connected to a shaft 110 by a coupling sleeve 112. The shaft 110 is journaled in bearings 114 in the gear box 78 and has a gear 116 fixed thereto. The gear 116 is engaged with another gear 118 fixed to a first intermediate shaft 120 also journaled in bearings 122 for rotation in the gear box 78. The first intermediate shaft 120 has a second gear 124 fixed thereon in mesh with a gear 126 fixed on a second intermediate shaft 128 journaled in bearings 130 in the gear box 78. The gear 126 is also in driving contact with a gear 80a that is fixed to the two portions 80b, 800 of the nut 80 which have a bore therethrough which is in threaded engagement with the lead screw 20. The gear 86a and the portion 80b, 80c comprise the nut 80 which is rotated to move the box frame 26 along the lead screw 20. The nut 80 is journaled in bearings 132 in the gear box 78. Thus drive from the hydraulic motor 82 is connected to the nut 80 through gears 116, 118, 124, 126, and 80a. All four of the nuts 80 engaged with the lead screws 20 are driven in the same manner as the nut 80 shown in FIG. 4.

It is seen in FIG. 4 that the shaft 110 is also coupled through a sleeve 134 to the hydraulic counterbalance motor 83 which produces a constant torque on the shaft 110 to produce a lifting force that opposes the lowering effect resulting from the weight of the box frame 26 and mechanism therein. All four of the counter balance motors 83 produce a similar torque, the total effect of which is to maintain the box frame effectively weightless with respect to the hydraulic motors 82 which move the box frame 26 on the lead screws 20.

Each of the synchros 81 (FIG. 3) are connected to a second intermediate shaft 128 as shown in FIG. 4 by gearing 136, 138 for rotation when the nut is rotated by the motor 82. These synchros 81 are connected electrically to hydraulic servo control means of well known construction to maintain identical operation of each of the four motors 82. This arrangement maintains a proper movement of the box frame 26 without a tendency for it to become cocked on the ways 16, 18 (FIG. 3).

Inside the box frame 26 (FIG. 3) and fixed to the front and rear rails 66 are a pair of horizontal ways 84 which are transverse to the axis of the driving plate 14 and which straddle that axis at the front and rear of the machine. These ways 84 are adapted to support the tool carriers 88, and are embraced in channel ways in the carriers 88, 90 to provide guidance for transverse movement thereof. (Carrier 90 is shown advanced toward the axis of rotation of the driving plate 14 in FIG. 3.) The swivel spindles 30 are supported in the carriers 88, 90 and are pivotally adjustable therein. The carriers 88, 90 are threadedly engaged with horizontal positioning screws 92 which are rotatably received in bearing journals 94 received in the side members 70 between the plates 72, 74 thereof. At the end of the positioning screws 92, fixed to the side members 70, are gear boxes 96 and motors 98 (FIGS. 1 and 3) which are operative to rotate the positioning screws 92 to effect transverse positioning of the carriers 88, 90 for movement of the tools 28 toward and away from the axis of rotation of the driving plate 14.

From the construction of the box frame 26 and the reception of the tools 28 therein, it can be seen that reactive forces produced on the tools 28 during a metal spinning operation are transmitted through the positioning screws 92 and horizontal ways 84 to the box frame 26. The forces transmitted through the positioning screws 92 produce opposing tension stresses in the front and rear rails 66. The forces transmitted through the horizontal ways 84 create bending forces in the front and rear rails 66 due to forces which tend to rotate the box frame 26 about a horizontal axis during the operation. The box frame construction is strong enough to absorb the stresses produced by these forces without excessive distortion. Consequently, the deflection of the vertical guide ways 16, 18 is reduced since the reactive forces transmitted thereto are equal only to the unbalance of forces on the box frame 26. The bearing pressures on the vertical guide ways .16, 18 are similarly reduced, being proportional to the deflective forces transmitted to the guide ways 16, 18.

The construction of .the tailstock unit 34 (FIG. 1) is analogous to that of the box frame 26. It is basically of rectangular shape having brackets at the front and rear in which gear boxes 102 which include rotatable nuts 104 engaged with the lead screws 20 are included. The tailstock unit 34 is supported and moved on the lead screws 20 by the nuts 104. The nuts 104 are rotated by operation of motors 106, one in front and one in the rear, each of the motors 106 being connected for simultaneous rotat-ion of two of the nuts 104. The front and rear motors 106 are synchronized for cooperative operation to maintain the t-ailstock unit 34 square with the vertical guide Ways 16, 18 which are embraced by the tailst-ock unit 34 in a manner similar to that of the box frame 26. The tailstock unit carries the spindle 36 which is positionable to rotate on the same axis as the driving plate 14. The spindle 36 is adapted to receive and hold a spindle extension 108 (FIG. 1) which is designed to engage and hold a workpiece on the mandrel 32 during certain spinning operations. The extension 108 is long enough to provide clearance between the tailstock unit -34 and the base :10 for movement of the tools 28 along the full operating length of the mandrel 32.

In operation of the machine, a workpiece blank of a general disc shape, for example, would be placed on top of the mandrel 32 (FIG. 1) and the tailstock 34 lowered until the extension 108 engaged the workpiece blank to hold it firmly against the top of the mandrel 32. The driving plate 14 to which the mandrel would be firmly bolted by use of the T-slots 110 therein (not all shown in FIG. 2) would then be rotated. The box frame 26 would be at a starting position above the mandrel 32 and below the tailstock 34. The tools 28 would be swiveled to a position similar to that shown in FIG. 3 and transversely positioned in the box frame 26 so that as it is moved downward by operation of the motors '82 the tools 28 would begin to force the metal disc to conform to the shape of the mandrel 32. As the tools 28 contact the workpiece, the positioning screws 92 would be rotated by the motors 98 to allow the tools 28 to follow the mandrel contour and exert approximately equal forces on the workpiece. The motors 98 might be controlled by either a tracer and template mechanism or by a program control, both of any well known form. As previously pointed out, the reactive forces transmitted from the tools 28 to the box frame 26 would be absorbed therein without excessive distortion since the box frame is of strong and rigid construction. Moreover, by maintaining the forces approximately equal on each tool 28, the box frame 26 would have a self-centering effect around the axis of rotation of the driving plate 14. The combination of the reduced distortion in the box frame 26 and the self-centering effect produced by balanced forces on the tools 28 would significantly reduce vertical guide way deflection and bearing pressure. Accurate position control of the tools 28 relative to the axis of rotation is facilitated thereby and closer tolerances in wall thickness and finish of a workpiece may be maintained.

It is also pointed out that in the use of the machine in a spinning operation requiring the use of only one tool, the box frame 26 is effective to transmit the reactive forces to all four of the columns 12 and not to just two of them. This feature provides more machine rigidity in the single tool operation and the strength requirement of the columns 12 is reduced with a corresponding saving in material and machine weight since all columns are used, even in single tool operation.

What is claimed is:

1. A metal spinning machine for shaping a workpiece around a mandrel concentric with a vertically oriented axis of rotation comprising, a machine base having a driving member therein adapted to receive and rotate said mandrel on said axis, a plurality of spaced columns extending from said base having guide ways thereon parallel to said axis, a plurality of spaced lead screws extending from said base parallel to said axis, a rigid box frame held in alignment around said axis by said guide ways, said box frame having ways therein transverse to said axis and having a plurality of lead screw nuts, each not engaged with one of said lead screws, to support the weight of said box frame over said base, a plurality of spin forming tools adapted to force a workpiece, received on said mandrel and rotating therewith, to conform to the shape of said mandrel when said tools are forced into forming contact with the workpiece, said tools received in said box frame on said ways therein for transmission of reactive forces to said box frame tending to balance one another when said tools are in forming contact with the workpiece, means to effect relative rotation between said lead screws and the respective nuts engaged therewith for movement of said box frame along said guide ways, means to effect a constant force tending to produce relative rotation between said lead screws and the respective nuts engaged therewith to counter balance the weight of said box frame, and means to move said tools on said ways in said box frame, said means to move said tools and means to effect relative rotation coacting to effect forming contact between said tools and the workpiece.

2. A metal spinning machine for shaping a workpiece around a mandrel concentric with a vertically oriented axis of rotation comprising, a machine base having a driving member therein adapted to receive and rotate said mandrel on said axis, a plurality of spaced columns extending from said base having guide ways thereon parallel to said axis, a plurality of spaced lead screws extending from said base parallel to said axis, a rigid box frame held in alignment around said axis by said guide ways and supported on said lead screws, said box frame having ways therein transverse to said axis, a plurality of spin forming tools adapted to force a workpiece, received on said mandrel and rotating therewith, to conform to the shape of said mandrel when said tools are forced into forming contact with the workpiece, said tools received in said box frame on said ways thereinto transmit reactive forces to said box frame tending to balance one another when said tools are forced into forming contact with the workpiece, means to move said tools on said Ways in said box frame, means cooperative with said lead screws to move said box frame along said guide ways, said means to move said tools and said means to move said box frame coacting to effect forming contact between said tools and the workpiece, a tailstock, adapted to stabilize rotation of said mandrel and workpiece, supported on said lead screws above said box frame and held in alignment with said axis by said guide ways, and means cooperative with said lead screws to effect vertical positioning of said tailstock relative to said base.

3. A metal spinning machine for shaping a workpiece around a mandrel concentric with a vertically oriented axis of rotation comprising, a machine base having a rotatable driving plate therein adapted to receive and rotate said mandrel on said axis, a plurality of spaced columns extending from said base having guide ways thereon parallel to said axis, a plurality of spaced lead screws fixed to and extending from said base parallel to said axis, a rigid box frame held in alignment around said axis by said guide ways, said box frame having a plurality of rotatable lead screw nuts received therein and engaged with said lead screws for support over said base and having ways therein transverse to said axis, a plurality of spin forming tools adapted to force a workpiece, received on said mandrel and rotating therewith, to conform to to the shape of said mandrel when said tools are in contact with the workpiece, said tools received in said box frame on said ways therein for transmission of reactive forces to said box frame tending to oppose one another when said tools are in forming contact with the workpiece, means to rotate said nuts in said box frame and elfect movement of said box frame along said guide ways, means to move said tools on said ways in said box frame, said means to move said tools and said means to rotate said nuts coacting to effect forming contact between said tools and the workpiece, a tailstock, adapted to stabilize rotation of said mandrel and workpiece, having a plurality of rotatable lead screw nuts received therein and engaged with said lead screws for support over said base, said tailstock held in alignment with said axis by said guide ways, and means to rotate said nuts in said tailstock and effect positioning of said tailstock relative to said base.

4. A metal spinning machine for shaping a workpiece around a mandrel concentric with a vertically oriented axis of rotation comprising, a rectangular machine base having a vertically extending column at each corner thereof, each column having guide ways thereon parallel to said axis, said base also having, within the perimeter thereof, a rotatable driving plate adapted to receive and rotate said mandrel on said axis, a set of lead screws cfixed to said base and extending therefrom parallel to said axis, one lead screw of said set adjacent to each of said columns, a rigid box frame held in alignment around said axis by said guide ways, said box frame having a plurality of lead screw nuts received therein and engaged with said lead screws for support over said base and having a pair of spaced ways therein transverse to and on opposite sides of said axis, a pair of tool carriers re ceived across said ways in said box frame on opposite sides of said axis, each of said carriers movable transversely relative to said axis and having a spin forming tool adapted to force a workpiece, received on said mandrel and rotating therewith, to conform to the shape of said mandrel when said tool is forced into forming contact with the workpiece, two pairs of rotatable adjusting screws, the screws of one pair axially fixed in one side of said box frame and engaged with one of said tool carriers, the screws of the other pair axially fixed in the opposite side of said box frame and engaged with the other of said tool carriers, said adjusting screws and pair of spaced ways operable to transmit reactive forces to said box frame tending to balance one another when both of said tools are in forming contact with the workpiece, horizontal drive motors operable to rotate said adjusting screws and move said tool carriers transversely relative to said axis, vertical feed motors on said box frame operable to rotate said nuts in said box frame and move said box frame along said guide ways, said vertical feed motors and said horizontal drive motors coacting to effect forming engagement between said tools and the workpiece, a tailstock adapted to stabilitze rotation of said mandrel and workpiece having a plurality of rotatable lead screw nuts received therein and engaged with said lead screws for support of said tailstock over said base, said tailstock held in alignment with said axis by saidguide ways, and tailstock motors operable to rotate said nuts in said tailstock to effect positioning thereof.

5. A metal spinning machine for shaping a workpiece around a mandrel concentric with a vertically oriented axisof rotation comprising, a rectangular machine base having a vertically extending column at each corner thereof, each column having guide ways thereon parallel to said axis, said base also having, within the perimeter thereof, a rotatable driving plate adapted to receive and rotate said mandrel on said axis, a set of lead screws fixed to said base and extending therefrom parallel to said axis, one lead screw of said set adjacent to each of said columns, a rigid box frame held in alignment around said axis by. said guide ways, said box frame having a plurality of rotatable feed nuts received therein and engaged with said lead screws to support the weight of said box frame over said base and a pair of spaced ways therein transverse to and on opposite sides of said axis, a pair of tool carriers received on said ways in said box frame on opposite sides of said axis, each of said carriers movable transversely relative to said axis and having a on said mandrel and rotating therewith, to conform to the shape of said mandrel when said tool is forced into forming contact with the'workpiece, two pairs of rotatable adjusting screws, the screws of one pair axially fixed in one side of said box frame and engaged with one of said tool carriers, the screws of the other pair axially fixed in the opposite side of said box frame and engaged with the other of said tool carriers, said adjusting screws and pair of spaced ways operable to transmit reactive forces to said box frame tending to balance one another when both of said tools are in forming contact with the workpiece, a set of horizontal drive motors, each of said drive motors operable to rotate one of said adjusting screws, said drive motors cooperating to move said tool carriers transversely relative to said axis, a set of vertical feed motors received on said box frame, each of said feed motors operable to rotate one of said feed nuts in said box frame,

said feed motors cooperating to move said box frame along said guide ways and coacting with said drive motors to effect forming engagement between said tools and the workpiece, a set of counterbalance motors received on said box frame and connected to said feed nuts, each of said counterbalance motors operable to apply a constant force to one of said feed nuts tending to produce rotation thereof in a direction to lift said box frame on said lead screws, said counterbalance motors cooperating to counterbalance the weight of said box frame, a tailstock adapted to stabilize rotation of said mandrel and workpiece having a plurality of rotatable positioning nuts re ceived therein, each of said positioning nuts engaged with one of said lead screws for support of said tailstock over said base, said tailstock held in alignment with said axis by said guide ways, and a set of tailstock motors operable to rotate said positioning nuts for movement of said tailstock relative to said base.

References Cited in the file of this patent UNITED STATES PATENTS 376,167 Seymour Jan. 10, 1888 1,262,780 Griffin Apr. 16, 1918 1,836,921 Harrison Dec. 15, 1931 2,975,743 Hoffman et al Mar. 21, 1961 FOREIGN PATENTS 820,564 Great Britain Sept. 23, 1959 

1. A METAL SPINNING MACHINE FOR SHAPING A WORKPIECE AROUND A MANDREL CONCENTRIC WITH A VERTICALLY ORIENTED AXIS OF ROTATION COMPRISING, A MACHINE BASE HAVING A DRIVING MEMBER THEREIN ADAPTED TO RECEIVE AND ROTATE SAID MANDREL ON SAID AXIS, A PLURALITY OF SPACED COLUMNS EXTENDING FROM SAID BASE HAVING GUIDE WAYS THEREON PARALLEL TO SAID AXIS, A PLURALITY OF SPACED LEAD SCREWS EXTENDING FROM SAID BASE PARALLEL TO SAID AXIS, A RIGID BOX FRAME HELD IN ALIGNMENT AROUND SAID AXIS BY SAID GUIDE WAYS, SAID BOX FRAME HAVING WAYS THEREIN TRANSVERSE TO SAID AXIS AND HAVING A PLURALITY OF LEAD SCREWS NUTS, EACH NUT ENGAGED WITH ONE OF SAID LEAD SCREWS, TO SUPPORT THE WEIGHT OF SAID BOX FRAME OVER SAID BASE, A PLURALITY OF SPIN FORMING TOOLS ADAPTED TO FORCE A WORKPIECE, RECEIVED ON SAID MANDREL AND ROTATING THEREWITH, TO CONFORM TO THE SHAPE OF SAID MANDREL WHEN SAID TOOLS ARE FORCED INTO FORMING CONTACT WITH THE WORKPIECE, SAID TOOLS RECEIVED IN SAID BOX FRAME ON SAID WAYS THEREIN FOR TRANSMISSION OF REACTIVE FORCES TO SAID BOX FRAME TENDING TO BALANCE ONE ANOTHER WHEN SAID TOOLS ARE IN FORMING CONTACT WITH THE WORKPIECE, MEANS TO EFFECT RELATIVE ROTATION BETWEEN SAID LEAD SCREWS AND THE RESPECTIVE NUTS ENGAGED THEREWITH FOR MOVEMENT OF SAID BOX FRAME ALONG SAID GUIDE WAYS, MEANS TO EFFECT A CONSTANT FORCE TENDING TO PRODUCE RELATIVE ROTATION BETWEEN SAID LEAD SCREWS AND THE RESPECTIVE NUTS ENGAGE THEREWITH TO COUNTER BALANCE THE WEIGHT OF SAID BOX FRAME, AND MEANS TO MOVE SAID TOOLS ON SAID WAYS IN SAID BOX FRAME, SAID MEANS TO MOVE SAID TOOLS AND MEANS TO EFFECT RELATIVE ROTATION COACTING TO EFFECT FORMING CONTACT BETWEEN SAID TOOLS AND THE WORKPIECE. 